The present invention relates to a liquid ejecting head, such as an ink jet type recording head, and more particularly, to a liquid ejecting head which is provided with a nozzle forming member having a plurality of nozzle orifices formed thereon and which can eject liquid from the nozzle orifices in forms of liquid droplets. The present invention also relates to a method of manufacturing such a liquid ejecting head.
As a liquid ejecting head which causes a pressure change of liquid within a pressure chamber so as to eject liquid droplets from the nozzle orifices, for example, an ink jet type recording head which is used in an image recording apparatus, such as a printer or the like, a color material ejecting head which is used for manufacturing a color filter of a liquid crystal display or the like, an electrode material ejecting head which is used for forming electrodes of an organic electroluminescent (EL) display, a field emission display (FED), or the like, a biological organic material ejecting head which is used for manufacturing a bio chip (biochemical element), and the like can be used.
Of various types of liquid ejecting heads, for example, an ink jet type recording head (hereinafter, referred to as recording head) in an ink jet type recording apparatus (hereinafter, simply referred to as printer) is provided with a head unit (head main body) having a flow passage unit, in which a liquid flow passage from a reservoir to nozzle orifices through a pressure chamber is formed, or an actuator unit having a pressure generating element which can change a volume of the pressure chamber, a metallic nozzle plate having nozzle lines, in which a plurality of nozzle orifices are provided to be connected with the liquid flow passage, and a head case, made of resin, to which the head unit and the nozzle plate (a type of nozzle forming member) are fixed.
In such a recording head, flight deviation may occur in liquid droplets to be ejected according to a state around the nozzle orifice, that is, a state in which liquid, such as ink or the like, wets around the nozzle orifice. That is, if liquid, such as ink or the like, wets around the nozzle orifice, liquid droplets are pulled by a surface tension of that part at the time of eject, which causes flight deviation. In general, in order to prevent flight deviation, a liquid repellent treatment for preventing adhesion of liquid, such as ink or the like, around the nozzle orifice is performed on a liquid ejecting surface of the nozzle plate.
The nozzle plate in the recording head is fixed to the head case by the metallic head cover having an exposure window, through which the nozzle orifices of the nozzle plate are exposed. The head cover has a function of protecting the head unit or the nozzle plate and preventing the individual parts from being separated. In addition, the head cover, which is set to a ground potential, comes into contact with the nozzle plate to be electrically connected thereto, thereby removing static electricity generated in recording paper or the like from the nozzle plate. Accordingly, for example, an inconsistency, such as an electrostatic breakdown of a driving circuit or the like caused by static electricity to be transferred through the nozzle plate, or an inconsistency, or an erroneous operation caused by the superimposition of the static electricity on a driving signal as noise can be prevented. Such a configuration is disclosed in, for example, Japanese Patent Publication Nos. 2004-74676A and 2000-190513A.
Recently, however, in such a printer, there is a tendency that pigment-based ink for improving image quality or water-resistant ink for improving water resistance is used. As a solvent of such ink, instead of water, a resin-based dispersing agent is used. For this reason, a liquid repellent coating layer, which is formed on the liquid ejecting surface of the nozzle plate so as to prevent defective eject, such as flight deviation caused by ink adhesion around the nozzle orifice, needs to have high liquid repellency according to such ink. Further, in order to reduce manufacturing costs by simplifying a coating treatment process, in addition to the significant improvement of liquid repellency or quality, the liquid repellent treatment is performed on the liquid ejecting surface of the nozzle plate, for example, using a thin film deposition technology. With the liquid repellent treatment, a liquid repellent coating layer, which contains more fluorine resin is formed on the liquid ejecting surface of the nozzle plate. However, if the content ratio of fluorine resin is increased in order to enhance liquid repellency, an insulation property of the liquid ejecting surface of the nozzle plate is increased accordingly, since fluorine resin has a high insulation property.
On the other hand, as the water repellent film with an improved water repellent performance, the use of a glassy insulating film has been examined, as described in Japanese Patent Publication No. 2004-351923A.
If such a liquid repellent coating layer or an insulating film is formed on the nozzle surface of the nozzle plate, the nozzle plate and the head cover face each other through the insulating film when the head cover is simply mounted as described the above, and thus the static electricity flying from the paper to the nozzle plate or the charges of the nozzle plate cannot be released through the head cover.